Arcturus Therapeutics Holdings Inc

Item 1A. Risk Factors.

Our business is subject to various risks, including those described in Item 1A of our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which we strongly encourage you to review. Except as disclosed below, there have been no material changes from the risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2025 filed with the Commission on March 3, 2026.

Geopolitical risks associated with ongoing wars and armThe termination of our collaboration with CSL Seqirus requires us to advance, fund, and seek partners for our vaccine programs, and subjects us to additional risks and uncertainties.

On August 3, 2026, we entered into a Termination and Settlement Agreement with CSL Seqirus pursuant to which we mutually terminated conflicts could have an adverse impact on our busthe CSL Collaboration Agreement, effective as of such date (the Termination Agreement). The CSL Collaboration Agreement provided CSL Seqirus with exclusive global rights to research, develop, manufacture, and commercialize mRNA vacciness, financial condi against COVID-19, influenza, and other infection us diseases using our STARR and results of operaLUNAR platform technologies. Under the CSL Collaboration Agreement, CSL Seqirus was responsible for leading development and commercializations, of vaccines including our clinical trials.

Geopo the licensed fields, and collaboration revenue has historically been a significant component of our total revenue. We now bear sole responsibiliticaly for all decisions regarding the developments related to ongoi, manufacturing, and commercialization of these vaccine products. We have limited experience commercializing globvaccine products independently, and we may need to build internal conflicts and tensions are sources of ummercial capabilities, enter into new partnerships, or engage distributors in order to maximize value of the assets, and there can be no assurancertainty and risk, and may that we will be able to do so on favorable terms or at all. Several of the vaccine programs are in early-stage development, which will require substantial additional cause disruptions to global or regional markets, supply chains or operapital and resources to advance. We do not expect to receive any further milestone payments, research funding, or profit-sharing payments under the CSL Collaboration Agreement. Under the Termination Agreement, we are also obligated to pay CSL Seqirus royalties and revenue-sharing on our future commercializations in applicable regions, of these vaccine products and successor products if such products are covered by CSL Seqirus royalty-bearing including those relatedtellectual property, which could reduce the profitability of our vaccine programs and make such programs less attractive to conflicts inpotential partners.

During the Middle East. We have Northern Hemisphere 2026-2027 season (expected to end June 30, 2027), CSL Seqirus and may Meiji Seika Pharma (Meiji) will continue to evaluatebe responsible for commercializing KOSTAIVE in Japan, and engage in activities, including engagfor future seasons, we will need to establish direct or indirect commercial arrangement of clinical sites, in s with Meiji or another distributor for the Japanese market, and any othe Middle East. Conflictsr markets. Any disruption in the Middle Easttransition of activities, supply, or regulatory responsibilities could disrupt operadversely affect sales of KOSTAIVE in Japan and damage our relations of companhips with key counterparties doing business in the region, includingand regulators. We have entered into a transition plan with CSL Seqirus for the orderly transfer of clinical trials, regulatory filings, in Israel. Any significant changes in the political, economic, financialtellectual property, and other materials, but there can be no assurance that such transition will be completed without delays or disruptions. We intend to evaluate strategic opportunities to maximize the value of the vaccine portfolio, including development, competmercialization, and partnering opportunitive, legal and regulatoryes, but there can be no assurance that we will identify suitable partners or reimbursenter into collaboration arrangement conditions where we conduct, or plan to expand, s on favorable terms. The pursuit of multiple early-stage vaccine programs in parallel could strain our financial and operational resour internatces and divert management attentional operations may  from our rare disease therapeutic programs, which are our primary area of focus, and could have a material adverse impact on our business, financial condition or r and results of operations.

22